1. Field of Invention
This invention relates to fluorescent lamps and ballasts and more particularly to a device that works with a ballast for starting and flashing fluorescent lamps.
2. Description of Related Art
Fluorescent lamps are used to provide illumination in various applications such as offices, signs and machinery. The fluorescent light is typically continuously operated in a steady state mode with a constant level of light output. In some applications, it is desirable to flash the fluorescent lamp to act as a signaling device. One such application is in gaming devices. Gaming devices are typically equipped with displays that have a fluorescent lamp located behind a light transmitting panel. In order to promote special operations or bonus opportunities, the fluorescent lamp is flashed.
A fluorescent lamp cannot be turned on and off like a conventional light bulb. The fluorescent lamp is connected to a device called a ballast. The ballast provides a high striking voltage required to initiate an arc across the lamp tube and regulates the current flowing through the arc after it has been struck. One possible solution is to use a new ballast design such as an electronic ballast that supports flashing. A problem with using an entire new type of ballast is that it adds cost and complexity to the machine when it is manufactured or retrofitted. Further, many gaming devices have been, and continue to be, manufactured for non-flashing operation only.
U.S. Pat. Nos. 6,043,615 and 5,854,542 issued to Forbes disclose a device for flashing of fluorescent lamps in a gaming device. The Forbes device uses a DC switched transistor to replace the glow bulb assembly in conventional magnetic ballast. During initial lamp startup, the transistor is on, allowing current to flow through the lamp filaments and heating to occur. Next the transistor is turned off, allowing the ballast inductor to have an inductive voltage spike of approximately 500 volts. The voltage spike in conjunction with the heated filaments is sufficient to ionize the gases in the lamp tube and cause an arc to strike thus lighting the lamp. When the transistor is turned on again, the current preferentially flows through the transistor instead of the arc and the arc is extinguished. Forbes claims that the transistor can be switched to dim the fluorescent lamp. However, the Forbes device has several drawbacks. First, dimming the lamp by repeatedly switching the lamp on and off causes the emissive coating on the lamp filaments to be blasted off and leads to premature lamp failure. Second, the Forbes device is limited in its power handling capabilities to less than 22 watts. When Forbes is used to switch a circuit with a greater amount of power, the transistor is pulled out of saturation and falls into an ohmic state. This causes the transistor to operate as an amplifier, which produces a significant amount heat.
What has long been needed is a device for flashing fluorescent lamps that is adapted to handle a relatively greater amount of power. This would allow multiple lamps to be flashed with the same device. Another long felt need is for a device that can flash fluorescent lamps that is readily usable with currently installed ballasts and that can be manufactured at a low cost. A further long felt need is a device for flashing fluorescent lamps that allows for long lamp life.
1. Advantages of the Invention
An advantage of the present invention is that it provides a circuit to repeatedly flash fluorescent lamps.
Another advantage of the present invention is that it provides a circuit that is adapted to flash florescent lamps with relatively high power requirements or multiple lamps.
Yet another advantage of the present invention is that it operates a lower temperature.
A further advantage of the present invention is that it provides a flashing circuit for fluorescent lamp ballasts that can be used with existing magnetic ballast.
An additional advantage of the present invention is that it provides a flashing circuit for fluorescent lamp ballasts that provides long lamp life.
These and other advantages of the present invention may be realized by reference to the remaining portions of the specification, claims, and abstract.
2. Brief Description of the Invention
The present invention comprises a circuit for flashing a fluorescent lamp. The circuit comprises a first and second terminal for coupling the circuit to a fluorescent lamp circuit. The terminals receive an AC power source. First and second switches are provided in series for switching the AC power source. The first and second switches are coupled between the first and second terminals. An isolation circuit is coupled to both the first and second series coupled switches. A control circuit is coupled to the isolation circuit. The control circuit controls the first and second series coupled switches in response to an external control signal. A control terminal is coupled to the control circuit in order to receive the external control signal.
The above description sets forth, rather broadly, the more important features of the present invention so that the detailed description of the preferred embodiment that follows may be better understood and contributions of the present invention to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and will form the subject matter of claims. In this respect, before explaining at least one preferred embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and to the arrangement of the components set forth in the following description or as illustrated in the drawings. The invention is capable of other embodiments and of being, practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.